An Adelaide-Darwin railway and naval-base supply

How would completing the Adelaide-Darwin railway in 1955 affect Darwin as a naval base?

Rail access would improve supply from the rest of Australia and reduce dependence on shipping.

A railway connection would improve Darwin's viability as a naval base by bringing supplies from the rest of Australia overland. Sea transport would remain available, but it would no longer be the sole route for supporting the base. Better access is also suggested as a reason to invest in stronger air defences. The question specifies hypothetical completion in 1955, while the later air-attack reference has an unresolved chronology.